import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

public class StudentManager {
    private List<Student> students;

    public StudentManager() {
        this.students = new ArrayList<>();
    }

    public void addStudent(Student student) {
        students.add(student);
    }

    public Student getStudentById(String studentId) {
        return students.stream()
                .filter(student -> student.getStudentId().equals(studentId))
                .findFirst()
                .orElse(null);
    }

    // 这里可以添加更多的管理方法，如删除、修改、查询等
}